The present invention relates generally to empty/load devices and, more specifically, to empty/load devices in electric-controlled pneumatic (ECP) brake systems.
On trains operating with ECP braking, there exists a potential single point of failure related to the head end unit (HEU) commanding all cars to an erroneous empty or loaded car weight for the purpose of determining the proper brake cylinder pressure. This could lead to a potential unsafe condition in that the train may be either under- or over-braked.
The present industry specifications for ECP braking require a mechanism for the ECP HEU to command a train-wide empty or loaded state to all ECP car control devices (CCDs). For cars not equipped with a load sensing device, the CCDs use this command to adjust brake cylinder pressure to provide the proper braking force based on total car weight. For example, on certain types of cars, the emergency brake cylinder pressure value could be 36 psi for an empty car and 77 psi for a fully loaded car. This results in approximately 50% more braking force when the car is loaded as compared to when the car is empty.
The command signal from the HEU is transmitted whenever there is a change of empty/load state, as requested by the train operator, and once every 120 seconds during normal train operations. Current ECP industry specifications allow a change to either empty or loaded while the train is stopped and allow a change only from empty to loaded when the train is in motion. Because there is a single command to set the state of the entire train, potential single point of failures exist that could cause this signal to be commanded erroneously. These failure modes include the following:
1) The trainline empty/load command signal fails to the improper state.
2) The HEU fails to command the empty/load signal when the train operator requests a change.
3) The ECP system operator interface fails to allow the proper empty/load selection.
4) The train operator fails to request the proper empty/load state for the train.
The present method of controlling the empty/load setting on cars having electropneumatic brakes addresses these problems. A first signal is set to an empty/load status. The first signal and a second signal is transmitted to the cars. The cars set their empty/load status to the status and in response to the receipt of both signals. The cars transmit their empty/load status, and the empty/load status of the cars is received and displayed.
The first signal is sent periodically, whereas the second signal is sent after the empty/load status of the first signal is confirmed. The display not only displays the cars"" empty/load status, but it also displays the current empty/load status of the first signal.
A prompt may be provided for the empty/load status to be confirmed for various conditions. These generally include: (1) after the train has been stopped; (2) after the train has slowed down to a predetermined speed, which is an indicia of loading/unloading of the cars; or (3) after the cars have been loaded/unloaded. The prompts can come from train speed control systems and/or loading/unloading systems. Also, the train speed control systems and the loading/unloading systems may automatically change the empty/load status.
These and other aspects of the present invention will become apparent from the following detailed description of the invention, when considered in conjunction with accompanying drawings.